Using a constant-current/constant-voltage algorithm, the stand alone charger can deliver up to 950 mA from the wall supply, or up to 500 mA from a USB supply. Float voltage accuracy is &plusmn0.6 percent. The charger is thermally regulated.

The LTC3550's synchronous buck regulator, which delivers up to 600 mA from a 2.5- to 5.5-volt input, features adjustable output voltage from 5.5 volts to as low as 0.6 volt. Operating efficiency is as high as 96 percent. Its automatic Burst Mode circuitry optimizes efficiency at light loads; quiescent current is just 20 microamps (less than 1 microamp in shutdown). The chip's high switching frequency (1.5 MHz) facilitates use of small low-cost (external) capacitors and inductors. The regulator is stable with ceramic output capacitors, achieving low output voltage ripple.

Click here for the product datasheet. The LTC3550 is priced starting at $2 each in 1k quantities.